1. Field of the Invention
In recent years considerable interest in isatoic anhydride has developed because of the facility with which it and its ring substituted analogues can be used as intermediates in the production of pharmaceuticals*, agricultural chemicals**, and anthranilic acid esters which are used as perfume essences and flavoring materials. Such interest has stimulated a search for new, less expensive and non-hazardous methods of production of isatoic anhydride and its substituted analogues. FNT * U.S. Pat. Nos. 3,170,955 (1965); 3,162,684 (1964); 3,163,646 (1964); 3,120,523 (1964); Neth. Apl. 6,407,857 (1965) U.S. Pat. Nos. 3,252,986 (1966); 3,274,194 (1966); FNT ** British 894,435 (1962); British 865,735 (1961); U.S. Pat. No. 3,244,503 (1966); Germany 1,210,242 (1966).
Many of the pyrimidinediones and ring substituted analogues formed by the method of the invention are useful as agricultural chemicals, in particular as herbicides. Specifically, many of the compounds have been found to have utility as plant growth regulators, total herbicides, selective weed killers, and defoliating agents.
In recent years increased crop yields have been made possible by the development and use of chemicals which are specifically toxic to weeds, yet do not damage crops around which they are applied. In general, the currently available chemicals which are most desired for their selectivity and as total herbicides are sufficiently expensive that cost is a significant factor in their use. Therefore, new compounds and inexpensive methods for producing such compounds are constantly being sought. The use of 3-substituted pyrimidine-diones is disclosed in application Ser. No. 740,090 filed June 26, 1968, now abandoned.
In addition, while many compounds presently on the market are effective against certain species of weeds, they are ineffective against others, or against certain strains of weeds. Apparently, resistant strains develop by a phenomenon which can be likened to "natural selection". Thus new herbicides which have broad spectrum effectiveness against a wide variety of weeds are continually being sought.
It is an object of the present invention to provide an improved method for producing heterocyclic acid anhydrides and pyrimidinediones.
It is a further object to provide a method for the production of heterocyclic acid anhydrides and pyrimidinediones which is non-hazardous and simple, and which does not require exotic or expensive starting materials or complicated apparatus.
It is a further object of the invention to provide an easy one-step method for the production of compounds having the following formulas: ##SPC1##
Wherein each of W, X, Y and Z is N or CH and, in the acid anhydride, not more than one of X, Y and Z is N, while, in the pyrimidinediones, not more than two of W, X, Y and Z can be N, and R is hydrogen or an alkyl group having not more than 8 carbon atoms.* FNT * Alkyl group is used in the ordinary sense of the word to indicate a straight-chain alkyl group.